For a long time, it has been standard to identify the authenticity of coins by using mechanical means such as a permanent magnet, and recently also electronic means, as a means of identifying the material quality and other properties of coins.
In such an apparatus, a coin sensor is provided along a coin path that is arranged within the coin-identifying apparatus, the electromagnetic characteristics of a coin falling down this coin path is checked, and the authenticity of the coin is determined therefrom.
One type of coin sensor that is used is an excitation means for magnetizing the coin and a means that detects the electromagnetic response of the magnetized coin, and the value detected in this way is analyzed to identify the authenticity of the coin.
One example of the conventional electronic coin-identifying means that could be cited is Japanese Patent Laid-Open No. 1989-193988 (Laid Open date: Aug. 3, 1989). Japanese Patent Laid-Open No. 1989-193988 discloses a method for rejecting counterfeit coins that closely resemble genuine coins.
A conceptual diagram of the prior art technique disclosed by Japanese Patent Laid-Open No. 1989-193988 is shown in FIG. 7. This figure illustrates the condition of a partial intrusion into a genuine-coin identification region 12 (solid lines) of a counterfeit distribution region 13 (broken lines). A triangular rejection region (shown hatched in the figure) is provided in order to identify and reject test coins that partially intrude into the genuine-coin identification region 12, and calculations are performed using function equations in order to determine whether or not test coins lie within the genuine-coin identification region. Each test coin is determined to be either genuine or a counterfeit by comparing the results of these calculations with predetermined reference values for specific denominations.